2．suitable　考查词性转换。此处表示"一个合适的时间"，应用形容词作定语修饰名词time。故填suitable。

　　3．requirement　考查词性转换。此处表示"一个合法的要求"。形容词legal用来修饰名词，其前有冠词a，故用require的名词形式requirement。

　　4．safely　考查词性转换。此处表示"安全地过马路"，应用副词修饰动词短语cross the road，故用safe的副词形式safely。

　　5．to　考查介词。appeal to意为"吸引"，为固定短语。故填to。

　　6．the　考查冠词。"the＋形容词"表示一类人。the retired意为"退休的人"，符合语境。故填the。

　　7．who　考查定语从句的引导词。空格处引导非限制性定语从句，在从句"__7__ had previously run crossing patrols (巡逻)"中作主语，指人，应用关系代词who引导从句。

　　8．saying　考查非谓语动词。空格处作后置定语，say与被修饰的名词"red and black rectangles"之间为主动关系，意为"写着"。故填say的现在分词形式saying。

　　9．to assist　考查非谓语动词。allow sb. to do sth. 意为"允许某人做某事"，是固定结构。故填to assist。

　　10．replaced　考查非谓语动词。此处表示"看见单词'children'被一个符号代替"，replace与saw的宾语"the word"之间为被动关系，故用replace的过去分词形式，作saw的宾语补足语。故填replaced。

　　Ⅳ.短文改错

Last month, I, as well as my parents, were invited to my uncle's home in the United States. My uncle, moved to America when I was five, has been living there for nearly ten years. She met us at the airport. I was exciting when I set my foot on the land of America. In the followed days, we visited some places of interest and took photos in the front of the Statue of Liberty. We all enjoyed visiting the Museum of Natural History so it enriched our knowledge great. For me, this is one of the most